Electric and hybrid vehicles have recently become a more common sight on roads worldwide. They have one thing in common and that is they all require a large and powerful rechargeable energy storage, e.g. a battery. In most such batteries, several battery cells are stacked together to form a battery powerful enough to provide energy for the vehicle to drive for example several tens of kilometers. The battery cells are in most cases mechanically fixed together with a common frame or enclosure to form a single unit which is conveniently mounted in the vehicle. Furthermore, the size of a battery providing sufficient power for driving an electric or hybrid energy is relatively large, whereby the battery cells tend to be closely packed in order to reduce the size of the battery.
However, the highly powerful batteries also produce high amounts of heat when in operation. Therefore, an appropriate cooling system is required for transporting heat away from the battery cells in order to prevent that the battery cells or other parts of the battery are damaged from overheating. The heat may for example be transported away from the battery cells by a liquid coolant passed through a cooling system in thermal contact with the battery cells. Alternatively or complimentary, cooling may be achieved by an air cooling system.
A battery typically comprises a number of stacked battery cells held together to form a unit. Typically, several modules comprising both battery cells and cooling systems are formed and subsequently mounted together. The mounting are not only meant for holding the modules or cells together but also to prevent swelling of the battery cells after successive operation.
One example of a battery is disclosed by US2012/0156537. The battery has battery cells stacked in parallel in a common direction. The stack of battery cells form a cell block and is held together by a tensioning device in the form of a screw with and a nut arranged through the stack. Several cell blocks are mechanically held together with bolts arranged through holes of tabs projecting from the cell blocks. However, such arrangement comprises relatively many parts and may further not obtain sufficient prevention of swelling of the battery cells at the same time as maintaining required cooling of the battery cells.
Therefore, it would be desirable to provide an energy storage device with more efficient assembly without compromising the performance of the energy storage.